Landing gear is the system that lets an aircraft roll, take off, land, taxi, and stop safely on the ground. In a tricycle landing gear layout, two main gear support most of the weight near the center of gravity, while a nose gear supports the front and helps steer. Landing gear matters because touchdown forces can be much larger than the aircraft weight for a short time.
A good gear system spreads these loads into the airframe while keeping the airplane stable and controllable.
Key Facts
- Tricycle landing gear has two main gear plus one nose gear, which improves forward visibility and reduces the chance of tipping forward.
- On most aircraft, the main landing gear carries the largest loads during landing, braking, and taxiing.
- Touchdown impact energy can be estimated with KE = 1/2 mv^2, where v is the vertical sink speed at landing.
- An oleo strut absorbs shock by compressing gas and forcing hydraulic fluid through small openings.
- Braking force depends on tire grip: F_friction = μN, where μ is the coefficient of friction and N is the normal force on the tire.
- Anti-skid braking reduces brake pressure when a wheel is about to lock, helping the tire keep rolling traction.
Vocabulary
- Tricycle landing gear
- A landing gear arrangement with two main gear near the middle of the aircraft and one steerable nose gear at the front.
- Oleo strut
- A shock absorber that uses compressed gas and hydraulic fluid to cushion landing loads.
- Main landing gear
- The strongest landing gear assemblies that carry most of the aircraft weight and usually contain the main wheel brakes.
- Nose gear
- The front landing gear assembly that supports the nose of the aircraft and often provides steering during taxi.
- Anti-skid system
- A braking control system that prevents wheel lockup by adjusting brake pressure to maintain tire traction.
Common Mistakes to Avoid
- Assuming the nose gear carries most of the landing load, which is wrong because the main gear is designed to take the heaviest touchdown and braking forces.
- Thinking landing gear only holds the airplane up, which is wrong because it also absorbs shock, steers during taxi, retracts on many aircraft, and helps stop the aircraft.
- Treating oleo struts like simple springs, which is wrong because their damping action comes from hydraulic fluid flow as well as gas compression.
- Using maximum braking without considering tire grip, which is wrong because locked wheels can skid and reduce control instead of shortening the stop.
Practice Questions
- 1 A small aircraft has a mass of 1200 kg and touches down with a vertical sink speed of 2.0 m/s. Estimate the vertical kinetic energy that the landing gear must absorb using KE = 1/2 mv^2.
- 2 During braking, each of two main wheels supports a normal force of 5500 N. If the tire runway friction coefficient is 0.65, what is the maximum total braking force from the two main wheels using F = μN?
- 3 Explain why a tricycle landing gear aircraft is usually more stable and easier to control on the ground than an older tailwheel design.